Brake systems for vehicles and other equipment with rotating wheels now widely include brake disks (also called rotors in U.S. English), which are located behind the wheel disk where they are attached to the wheel hub and fitted with brake lining. During braking, intense friction between the brake disk and the respective friction lining creates a significant amount of thermal energy, which causes a significant increase in temperature, especially of the brake disk. Excessive increase in temperature can cause serious defects of the brake system, which also reduces the operational safety of the vehicle or the given equipment operation. It may in particular result in shape distortion and even warping of the brake disk, brake disk rupture or melting. Fixing these defects or their prevention is connected with the need to replace brake disks, brake lining, etc., which represents a considerable cost, time burden and the need for a temporary decommissioning. Therefore, the brake disk cooling issues received considerable attention.
Formula One, racing cars, sports cars and airplanes are devices in which this issue is particularly significant. For these types of transport means, the operating temperature when braking from high speed reaches up to 1000° C., and thus the need for fast and high quality cooling of brake disks is urgent. This are specific equipments, in which case repair may be performed only by dedicated specialized workplaces, and it is therefore necessary either to get supplementary service centre, or drive off long distances for repairs, which increases cost and time requirements for the owner or the operator of these means of transport. Shutdown of operation here is particularly undesirable, and the need for reliability even in extreme loads is particularly high.
Cooling of brake disks is usually achieved by means of directed streams of cooling air. Its supply to the disk is effected through an air catcher, which contains a system of air channels that are emptied into the wheel hub. The wheel hub contains at least one air channel for the passage of air, which is led into the centre of the brake disk. The structural design of brake disks is chosen so as to allow the cooling air flow through the body of the disk. Existing brake disks have no cover and therefore the cooling air flows through them directly into the space of the wheel disk, from where it has a free passage into the ambient space. Throughput (patency) of disks for air is currently achieved by means of axial systems of air channels passing through the solid body of the brake disk or by means of radial vanes created in a hollow disk, where only the space between these vanes is used for the passage of air. Radial vanes are straight or curved.
The abovementioned background art is described briefly for example in the application CZ PV 2006-202 of the {hacek over (S)}koda Auto a.s. company. This application proposes to achieve internal cooling of the brake disk by means of three types of channels that are created in the otherwise solid mass of the disk in the shape of a ring, namely axial channels, radial channels, and channels in the shape of a helix coiled around the radial axis o. In this case, brake disk takes the form of a ring, as a body in the shape of annulus between two cylindrical surfaces, i.e. the input cylindrical surface and the output cylindrical surface. The lateral walls of the disk are called there as lateral friction surfaces. The input cylindrical surface, the output cylindrical surface, and lateral friction surfaces are delimiting the body of brake disk. The brake disk is fixed in place of use by means of a flange. The input cylindrical surface and the output cylindrical surface are interconnected by the axis around which the helix is coiled, on which helix the centre of gravity of cross-sectional area of the radial cooling channel is located. Axial channels are connected with radial channels by means of the helix. The disadvantage of this solution is the abovementioned interconnection of all types of channels, because it causes mixing of cooling air streams, hot ones with cold ones, which significantly reduces cooling efficiency.
Construction of a known vane brake disk is described, for example, in CZ Pat. 140297. The brake disk is arranged as two plates having the shape of annular ring, which are connected by means of essentially radial ribs forming there vanes, between which a passage of cooling air is possible in the inter-vane space. There is a significant disadvantage there that the abovementioned design only allows a rectilinear flow of cooling air in the direction radially from the axis of rotation of the brake disk, which results in low cooling efficiency with the need for supply of high quantity of cooling air.